Tire building drums for applying a tread and belt package onto a tire carcass are well known in the art. The tire building process generally has a stage one assembly of a tire carcass made of air impervious inner layer, a pair of beads, an apex and a reinforcing ply extending between and wrapping around the beads to form ply turnups. This unvulcanized structure also has sidewall rubber and outer rubber components such as gum strips, chafers or chipper added to the cylindrically shaped green carcass.
In a second stage, the green or uncured cylindrical carcass is taken to a separate tire building drum wherein the beads are locked onto the drum moved axially to a proper bead width spacing and the carcass is toroidaly shaped by expanding the carcass using an inflatable bladder which allows the carcass to assume a shape more closely approximating a finished tire. At this point, belt or breaker reinforcements such as steel cord reinforcement belts are applied onto the carcass. Typically the adjacent belt layers have the cords oppositely oriented. Once the belt structure is applied, a layer of tread rubber is added to complete the assembly.
These building drums are as described in US 2006/0137806 capable of moving the center section radially outward while moving the beads axially inwardly. In “Method Of Making A Tire Using A High Crown Uni-Stage Building Drum”, the inventors proposed building a tire using a single drum assembly which allowed the ply turnup to be made as the tire ply was held vertically in the bead regions. This machine while exhibiting a good degree of novelty, added much complexity to the tire building as it required special means to clamp the tire shoulders to secure the carcass on assembly. Furthermore, it added significant cost to the apparatus.
The present invention described hereafter attempts to solve the problems of high complexity by providing a unique second stage tire building drum which allows a relatively small tire carcass having a large diameter to be made. More particularly, a machine specifically adapted to construct motorcycle tires of a diameter of 16 inches, 16.5 inches and 17 inches of different axial bead widths. This type of tire is very small in cross-sectional profile and this means there is very little room for the mechanical parts of the building machine to be located. Nevertheless, such tires require precise building capability and superior solid building surfaces would allow the tire to be made of the highest quality. The present invention solid deck building drum provides this ability as described below.